Low-noise-reduction microwave source

Abstract

The invention relates to the field of photoelectric instruments and equipment, discloses a low-noise-reduction microwave source, and aims to solve the problem that the requirement of the atomic frequency standard field for low phase noise cannot be met in the prior art. The present invention comprises: a laser for emitting an original optical signal; the optical amplifier is used for enhancing the intensity of the original optical signal; the light intensity modulator is used for modulating the enhanced light signal; the optical filter is used for filtering the modulated optical signal; the alkali metal atom gas chamber is used for generating a filtering effect on the filtered optical signal to generate a first optical signal; the photoelectric detector is used for converting the first optical signal into a first electric signal; the microwave filter is used for filtering the first electric signal; the electric amplifier is used for amplifying the filtered electric signal; and the microwave coupler divides the amplified electric signal into two paths based on a set phase difference. The positive feedback oscillation microwave source based on atomic spectrum filtering has the advantages of low phase noise and stable microwave frequency, and meets the requirement of the atomic frequency standard field for low phase noise.

Description

Technical Field

[0001] The present invention relates to the field of optoelectronic instrument equipment, and particularly to a low-noise microwave source. Background Art

[0002] Microwave source devices are an important part of modern electronic products or equipment, capable of providing microwave signals of various frequencies to meet various requirements in the fields of communication, metrology, and radar. There are mainly two methods for developing classical microwave sources: one is to multiply the frequency through a crystal oscillator and then obtain the required microwave signal through frequency division, frequency mixing, etc.; the other is to directly use a dielectric resonator at the required frequency point to construct a positive feedback resonant circuit to generate microwave signals. A relatively new method is to generate microwave signals through optical beat or using an optical frequency comb and other optoelectronic methods. The classical microwave source acquisition method cannot obtain excellent phase noise; although the optoelectronic microwave generation method has a high phase noise index, it is expensive and the microwave system volume is extremely large, which is not conducive to integration with atomic clocks. Although the existing technologies have reduced the phase noise of microwaves to a certain extent, they still cannot meet the requirements for low phase noise in the field of atomic frequency standards.

[0003] Therefore, a low-noise microwave source is proposed. Summary of the Invention

[0004] This specification provides a low-noise microwave source to solve the problem that although the existing technologies have reduced the phase noise of microwaves to a certain extent, they still cannot meet the requirements for low phase noise in the field of atomic frequency standards. The microwave source includes:

[0005] A laser for emitting an original optical signal and sending the original optical signal to an optical amplifier;

[0006] An optical amplifier for receiving the original optical signal, enhancing the intensity of the original optical signal to obtain an enhanced optical signal, and sending the enhanced optical signal to an electro-optical modulator;

[0007] An optical intensity modulator for receiving the enhanced optical signal and modulating the enhanced optical signal to obtain a modulated optical signal;

[0008] An optical filter for filtering the modulated optical signal to obtain a filtered optical signal and sending the filtered optical signal to an alkali metal atomic gas cell;

[0009] An alkali metal atomic gas cell for receiving the filtered optical signal based on a first interface of the alkali metal atomic gas cell, generating a filtering effect on the filtered optical signal to obtain a first optical signal, and then sending the first optical signal to a photodetector based on a second interface of the alkali metal atomic gas cell;

[0010] A photodetector for receiving the first optical signal, converting the first optical signal into a first electrical signal, and sending the first electrical signal to a microwave filter;

[0011] A microwave filter is used to filter a first electrical signal to obtain a filtered electrical signal and send the filtered electrical signal to an electrical amplifier;

[0012] The electrical amplifier is used to amplify the filtered electrical signal to obtain an amplified electrical signal and send the amplified electrical signal to a microwave coupler;

[0013] The microwave coupler is used to divide the amplified electrical signal into two paths based on a set phase difference. The first path is sent to an optical intensity modulator as a modulation signal, and the second path is output as a microwave signal.

[0014] In a preferred embodiment, the microwave source further includes:

[0015] A quartz thin film is connected to a third interface of an alkali metal atomic gas cell through a first interface of the quartz thin film, and is used to transmit helium gas in a buffer gas cell to the alkali metal atomic gas cell;

[0016] The buffer gas cell is used to connect a second interface of the quartz thin film, and based on the temperature difference between the buffer gas cell and the alkali metal atomic gas cell, transmit helium gas to the alkali metal atomic gas cell through the quartz thin film;

[0017] A temperature controller is used to control the temperatures of the alkali metal atomic gas cell, the quartz thin film, and the buffer gas cell.

[0018] In a preferred embodiment, the microwave source further includes a current controller;

[0019] The current controller is used to connect to a fourth interface of the alkali metal atomic gas cell and change the current in the alkali metal atomic gas cell.

[0020] In a preferred embodiment, the optical amplifier is an EDFA type amplifier or an SOA type optical amplifier; the working wavelength range of the optical amplifier and the working wavelength range of the optical intensity modulator both match the working wavelength range of the laser.

[0021] In a preferred embodiment, the optical filter is a narrowband optical filter; the working wavelength of the filter matches the atomic transition energy level of the alkali metal atomic gas cell.

[0022] In a preferred embodiment, the alkali metal atomic gas cell specifically includes:

[0023] The alkali metal atomic gas cell is a sealed glass bulb structure, and the internal filling gas includes rubidium metal and cesium metal; a coil is wound around the outer wall of the sealed glass bulb structure, and the coil is used to provide a static magnetic field.

[0024] In a preferred embodiment, the quartz thin film specifically includes:

[0025] The quartz thin film is fused with the glass pipe. When the quartz thin film is heated, the helium leakage rate will change.

[0026] In a preferred embodiment, the current controller specifically includes: by controlling the change of the current in the alkali metal atomic gas chamber, the interval of the atomic transition energy level in the alkali metal atomic gas chamber is changed, and then the absorption frequency range of the filtered optical signal is changed.

[0027] In a preferred embodiment, the buffer gas chamber specifically includes:

[0028] By changing the temperature difference between the buffer gas chamber and the alkali metal atomic gas chamber and changing the internal temperature of the quartz thin film, the amount of helium penetrating into the alkali metal atomic gas chamber is changed, and then the atomic collision amplitude is changed, so as to change the interval of the atomic transition energy level, and then change the absorption frequency range of the filtered optical signal.

[0029] In a preferred embodiment, the first optical signal generated by the alkali metal atomic gas chamber forms an oscillation loop after passing through a photodetector, a microwave filter, an electrical amplifier, a microwave coupler, an optical intensity modulator, and an optical filter loop.

[0030] The above at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0031] After the original optical signal emitted by the laser is enhanced by an optical amplifier, it is modulated by an optical intensity modulator and undergoes precise spectral selection through an optical filter. Finally, the modulated optical signal is introduced into the alkali metal atomic gas cell. Based on the atomic transition characteristics inside, the alkali metal atomic gas cell highly selectively absorbs and transmits optical signals of specific frequencies, thus achieving an extremely pure optical filtering effect. This process ensures that the generated first optical signal has extremely low phase noise. Subsequently, a photodetector converts this pure first optical signal into a first electrical signal, which is further purified by a microwave filter and amplified by an electrical amplifier, making the output microwave signal not only have low phase noise but also high frequency stability. A microwave coupler divides the amplified electrical signal into two paths, one of which is fed back to the optical intensity modulator as a modulation signal, forming a closed positive feedback loop. This enables the system to reach a stable oscillation state at the set microwave frequency. This not only meets the requirements for microwave signals in the field of atomic frequency standards but also significantly improves the applicability and accuracy of the microwave source in time-frequency standard applications. The present invention not only ensures the superiority of the microwave source in performance but also makes its structure more compact and easier to integrate with other precision instruments. In summary, the positive feedback oscillation microwave source based on atomic spectral filtering proposed by the present invention successfully solves the problems of high phase noise, poor frequency stability, and difficulty in integrating with atomic clocks in the prior art, and also has the advantages of low phase noise and high microwave frequency stability, representing an important advancement in microwave source technology. Description of the Drawings

[0032] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application.

[0033] Figure 1 Schematic diagram of a low-noise reduction microwave source provided by an embodiment of the present specification. Detailed Embodiments

[0034] To make the objectives, technical solutions, and advantages of the present application clearer, the technical solutions of the present application will be clearly and completely described below in conjunction with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0035] The following will detail the technical solutions provided by each embodiment of the present application in conjunction with the drawings.

[0036] Figure 1 A low-noise reduction microwave source provided by an embodiment of the present specification, see Figure 1, the microwave source of the present invention includes:

[0037] A laser for emitting an original optical signal and sending the original optical signal to an optical amplifier;

[0038] An optical amplifier for receiving the original optical signal, enhancing the intensity of the original optical signal to obtain an enhanced optical signal, and sending the enhanced optical signal to an electro-optical modulator;

[0039] An optical intensity modulator for receiving the enhanced optical signal and modulating the enhanced optical signal to obtain a modulated optical signal;

[0040] An optical filter for filtering the modulated optical signal to obtain a filtered optical signal and sending the filtered optical signal to an alkali metal atomic gas cell;

[0041] An alkali metal atomic gas cell for receiving the filtered optical signal based on the first interface of the alkali metal atomic gas cell, generating a filtering effect on the filtered optical signal to obtain a first optical signal, and then sending the first optical signal to a photodetector based on the second interface of the alkali metal atomic gas cell;

[0042] A photodetector for receiving the first optical signal, converting the first optical signal into a first electrical signal, and sending the first electrical signal to a microwave filter;

[0043] A microwave filter for filtering the first electrical signal to obtain a filtered electrical signal and sending the filtered electrical signal to an electrical amplifier;

[0044] An electrical amplifier for amplifying the filtered electrical signal to obtain an amplified electrical signal and sending the amplified electrical signal to a microwave coupler;

[0045] A microwave coupler for dividing the amplified electrical signal into two paths based on a set phase difference, the first path being sent to the optical intensity modulator as a modulation signal, and the second path being output as a microwave signal.

[0046] A quartz thin film is connected to the third interface of the alkali metal atomic gas cell through the first interface of the quartz thin film, and is used to transmit the helium gas in the buffer gas cell to the alkali metal atomic gas cell;

[0047] A buffer gas cell for connecting to the second interface of the quartz thin film and transmitting the helium gas to the alkali metal atomic gas cell through the quartz thin film based on the temperature difference between the buffer gas cell and the alkali metal atomic gas cell;

[0048] A temperature controller for controlling the temperatures of the alkali metal atomic gas cell, the quartz thin film, and the buffer gas cell.

[0049] A current controller for connecting to the fourth interface of the alkali metal atomic gas cell and changing the current in the alkali metal atomic gas cell.

[0050] To specifically describe a low-noise microwave source of the present invention, the following specific description is provided. The microwave source specifically includes:

[0051] A laser for emitting an original optical signal and sending the original optical signal to an optical amplifier;

[0052] An optical amplifier for receiving the original optical signal, enhancing the intensity of the original optical signal to obtain an enhanced optical signal, and sending the enhanced optical signal to an electro-optic modulator;

[0053] In this embodiment, the optical amplifier is an EDFA type amplifier or an SOA type optical amplifier; the working wavelength range of the optical amplifier and the working wavelength range of the optical intensity modulator are both matched with the working wavelength range of the laser.

[0054] An electro-optic modulator for receiving the enhanced optical signal and modulating the enhanced optical signal to obtain a modulated optical signal;

[0055] An optical filter for filtering the modulated optical signal to obtain a filtered optical signal and sending the filtered optical signal to an alkali metal atomic gas cell;

[0056] In this embodiment, the optical filter is a narrowband optical filter; the working wavelength of the filter is matched with the atomic transition energy level of the alkali metal atomic gas cell.

[0057] An alkali metal atomic gas cell for receiving the filtered optical signal based on the first interface of the alkali metal atomic gas cell, generating a filtering effect on the filtered optical signal to obtain a first optical signal, and then sending the first optical signal to a photodetector based on the second interface of the alkali metal atomic gas cell; when the microwave frequency of the filtered optical signal is consistent with the atomic energy level transition frequency, a certain spectrum cannot be absorbed and has the maximum light intensity.

[0058] In this embodiment, the alkali metal atomic gas cell is a sealed glass bulb structure, and the internal filling gas includes rubidium metal and cesium metal; a coil is wound around the outer wall of the sealed glass bulb structure, and the coil is used to provide a static magnetic field.

[0059] A photodetector for receiving the first optical signal, converting the first optical signal into a first electrical signal, and sending the first electrical signal to a microwave filter;

[0060] A microwave filter for filtering the first electrical signal to obtain a filtered electrical signal and sending the filtered electrical signal to an electrical amplifier;

[0061] An electrical amplifier for amplifying the filtered electrical signal to obtain an amplified electrical signal and sending the amplified electrical signal to a microwave coupler;

[0062] A microwave coupler is used to divide an amplified electrical signal into two paths based on a set phase difference. The first path is sent as a modulation signal to an optical intensity modulator, and the second path is output as a microwave signal.

[0063] In this embodiment, the microwave source further includes:

[0064] A quartz thin film is connected to the third interface of the alkali metal atomic gas cell through the first interface of the quartz thin film, and is used to transmit the helium gas in the buffer gas cell to the alkali metal atomic gas cell.

[0065] In this embodiment, the quartz thin film specifically includes: The quartz thin film is fused with a glass pipe. When the quartz thin film is heated, the leakage rate of helium gas will change. The alkali metal atomic gas cell and the buffer gas cell are sealed together through the quartz thin film, and the sealing method can be pyrotechnic or laser welding.

[0066] A buffer gas cell is used to connect the second interface of the quartz thin film, and based on the temperature difference between the buffer gas cell and the alkali metal atomic gas cell, transmit helium gas to the alkali metal atomic gas cell through the quartz thin film.

[0067] In this embodiment, the buffer gas cell specifically includes: By changing the temperature difference between the buffer gas cell and the alkali metal atomic gas cell, and changing the internal temperature of the quartz thin film, the amount of helium gas penetrating into the alkali metal atomic gas cell is changed, thereby changing the atomic collision amplitude, and thus changing the interval of atomic transition energy levels, and further changing the absorption frequency range of the filtered optical signal.

[0068] A temperature controller is used to control the temperatures of the alkali metal atomic gas cell, the quartz thin film, and the buffer gas cell.

[0069] In this embodiment, the microwave source further includes a current controller;

[0070] A current controller is used to connect to the fourth interface of the alkali metal atomic gas cell and change the current in the alkali metal atomic gas cell.

[0071] In this embodiment, the current controller specifically includes: The current controller changes the interval of atomic transition energy levels in the alkali metal atomic gas cell by controlling the change of the current in the alkali metal atomic gas cell, and further changes the absorption frequency range of the filtered optical signal.

[0072] In this embodiment, the first optical signal generated by the alkali metal atomic gas cell forms an oscillation loop after passing through a photodetector, a microwave filter, an electrical amplifier, a microwave coupler, an optical intensity modulator, and an optical filter loop. Due to the extremely narrow atomic spectrum, good stability, and high equivalent Q value of the loop, the generated microwave signal has extremely low phase noise. When it is necessary to adjust the microwave frequency, the current of the alkali metal atomic gas cell is changed by a current controller, thereby changing the interval of the atomic transition energy level, and rough frequency tuning can be achieved, with a tuning magnitude of dozens of kHz. For precise adjustment, the temperature difference between the alkali metal atomic gas cell and the buffer gas cell is changed, and the temperature of the quartz thin film is increased. The amount of helium gas penetrating from the buffer gas cell into the alkali metal atomic gas cell will increase, and the collision with the alkali metal atoms in the alkali metal atomic gas cell will intensify, resulting in a larger frequency shift caused by the collision, and thus affecting the frequency change. If it is necessary to change the frequency in the reverse direction, the above operation steps are opposite.

[0073] The above are only the embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A low noise reduction microwave source, characterized in that: The microwave source comprises: A laser, used for emitting an original optical signal and sending the original optical signal to an optical amplifier; An optical amplifier, used for receiving an original optical signal and enhancing the strength of the original optical signal to obtain an enhanced optical signal, and sending the enhanced optical signal to an optoelectronic modulator; An optical intensity modulator, used for receiving the enhanced optical signal and modulating the enhanced optical signal to obtain a modulated optical signal, and sending the modulated optical signal to the optical filter; An optical filter, used for filtering the modulated optical signal to obtain a filtered optical signal, and sending the filtered optical signal to the alkali metal atom gas chamber; The alkali metal atom gas cell is used to receive the filtered light signal based on the first interface of the alkali metal atom gas cell, filter the filtered light signal to obtain the first light signal, and then send the first light signal to the photoelectric detector through the second interface based on the alkali metal atom gas cell; a photoelectric detector, configured to receive a first optical signal, convert the first optical signal into a first electrical signal, and send the first electrical signal to a microwave filter; A microwave filter, used for filtering the first electrical signal to obtain a filtered electrical signal, and sending the filtered electrical signal to the electrical amplifier; An electrical amplifier, used for amplifying the filtered electrical signal to obtain an amplified electrical signal, and sending the amplified electrical signal to the microwave coupler; The microwave coupler is used to divide the amplified electrical signal into two paths based on a set phase difference, the first path is sent to the optical intensity modulator as a modulated signal, and the second path is output as a microwave signal.

2. A low noise reduction microwave source according to claim 1, characterized in that: The microwave source also includes: A quartz film is connected to a third interface of the alkali metal atom gas chamber through a first interface of the quartz film, and is used to transmit the helium gas in the buffer gas chamber to the alkali metal atom gas chamber; A buffer gas chamber, used for connecting to the second interface of the quartz film, and transmitting helium to the alkali metal atom gas chamber through the quartz film based on the temperature difference between the buffer gas chamber and the alkali metal atom gas chamber; The temperature controller is used to control the temperature of the alkali metal atom gas chamber, the quartz film and the buffer gas chamber.

3. A low noise reduction microwave source according to claim 2, characterized in that: The microwave source also includes a current controller; The current controller is used to connect to the fourth interface of the alkali metal atom gas cell and change the current in the alkali metal atom gas cell.

4. A low noise reduction microwave source according to claim 3, characterized in that: The optical amplifier is an EDFA type amplifier or an SOA type optical amplifier; the operating wavelength range of the optical amplifier and the operating wavelength range of the optical intensity modulator both match the operating wavelength range of the laser.

5. A low noise reduction microwave source according to claim 4, characterized in that: The optical filter is a narrow-band optical filter; the working wavelength of the filter matches the atomic transition energy level of the alkali metal atom gas chamber.

6. A low noise reduction microwave source according to claim 5, characterized in that: The alkali metal atom gas chamber comprises: The alkali metal atom gas chamber is a sealed glass bubble structure, and the gas filled inside includes rubidium metal and cesium metal; the outer wall of the sealed glass bubble structure is wound with a coil, and the coil is used to provide a static magnetic field.

7. A low noise reduction microwave source according to claim 6, characterized in that: The quartz film comprises: When the quartz film is heated, the leak rate to helium changes.

8. A low noise reduction microwave source according to claim 7, characterized in that: The current controller includes: the current controller changes the current of the alkali metal atom gas cell, thereby changing the interval of the atomic transition energy level of the alkali metal atom gas cell, thereby changing the absorption frequency range of the filtered light signal.

9. A low noise reduction microwave source according to claim 8, characterized in that: The buffer air chamber comprises: By changing the temperature difference between the buffer gas chamber and the alkali metal atom gas chamber and the internal temperature of the quartz film, the amount of helium gas penetrating into the alkali metal atom gas chamber is changed, thereby changing the atomic collision amplitude, thereby changing the interval of the atomic transition energy level, and thus changing the absorption frequency range of the filtered light signal.

10. A low noise reduction microwave source according to claim 9, characterized in that: The first optical signal generated by the alkali metal atom gas chamber forms an oscillation circuit after passing through a photoelectric detector, a microwave filter, an electric amplifier, a microwave coupler, a light intensity modulator and an optical filter loop.

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